1. Technical Field
The present invention relates to an antiviral agent that has an excellent effect on non-enveloped viruses (e.g., fish disease viruses such as viral nervous necrosis virus (NNV), aquavirnavirus (ABV) and red seabream iridovius (RSIV); feline calicivirus which is an infectious pathogen of cats; human pathogenic viruses such as Coxsackie virus and adenovirus), that is highly safe for the human body, and that contains as an active ingredient at least one selected from the group consisting of extracts of plants of the genus Diospyros containing tannin, catechins, wattle tannin, pentagalloyl glucose, coffee tannin, alkyl gallates, pyrogallol, organic acids and/or salts thereof, and also relates to an antiviral composition containing the antiviral agent and useful for disinfection and infection control against the viruses.
2. Background Art
In general, viral diseases are difficult to cure because antibiotics have no effect thereon and thus become a major problem for humans and animals such as domestic animals. It is still fresh in our minds that SARS and avian influenza have recently attracted interest, and viral diseases also become a major problem for cultured fishes. However, there is no effective curing method for non-enveloped viruses, while surfactants and alcohols are effective for enveloped viruses, and a main measure against the non-enveloped viruses is prevention by vaccines.
“The astringent juice of the persimmon” produced by fermenting an extract from a persimmon has been used as Chinese herbal medicine, such as an antihypertensive agent, in China for a long time and is also familiar to Japanese as folk medicine. The astringent juice of the persimmon is rich in tannin and is believed to have astringency (the property of contracting a tissue by combining to a protein or another substance), antimicrobial action, and deodorizing action. The structure and a purification method of tannin (condensed tannin) contained in Diospyros kaki can be found in the following two papers (Matsuo and Itoo, 1981a/1981b: Non-patent Literatures 1 and 2).
As a composition containing the astringent juice of the persimmon or tannin of persimmon, for example, there has been proposed an antimicrobial dental composition (JP 2005-232043 A: Patent Literature 1) prepared by covering an extract from the astringent juice of the persimmon with cyclodextrin to further improve handleability and antimicrobial properties, and an anticancer agent and an antipneumonic viral agent (JP 2004-331641A: Patent Literature 2) prepared by adding and mixing the astringent juice of the persimmon with a component such as a peptide polysaccharide contained in Reishi spore.
JP 2006-206558 A (Patent Literature 3) discloses an antimicrobial composition containing a tannin substance, a fatty acid ester, and a chelating agent (Claim 1). Examples of the tannin substance include tannic acid, pyrocatechin, gallic acid, persimmon tannin, tea tannin, and gall tannin (Claim 4). However, the efficacy of the antimicrobial composition is demonstrated only for tannic acid in Escherichia coli and Staphylococcus aureus (Examples), and Patent Literature 3 does not specifically disclose a technical idea that persimmon tannin among the tannin substances has marked antiviral properties for non-enveloped viruses and thus persimmon tannin is very important as a component of an antiviral composition.
JP 2006-306836 A (Patent Literature 4) discloses that specified phenol derivatives are effective as inactivators for various viruses and also discloses various gallates as the phenol derivatives. However, Patent Literature 4 does not disclose viruses of the genera Vesivirus and Rotavirus and only n-octyl gallate is used in examples.
In addition, the inventors have proposed an anti-norovirus agent for norovirus that causes food poisoning and infectious gastroenteritis, the agent using a persimmon extract, and an anti-norovirus composition containing the anti-norovirus agent (International Publication No. 08/153077 pamphlet: Patent Literature 5).    Patent Literature 1: JP 2005-232043 A    Patent Literature 2: JP 2004-331641A    Patent Literature 3: JP 2006-206558 A    Patent Literature 4: JP 2006-306836 A    Patent Literature 5: International Publication No. 08/153077 pamphlet    Non-patent Literature 1: MATSUO, Tomoaki and ITOO, Saburo (1981a): Comparative Studies of Condensed Tannins from Several Young Fruits. J. Japan. Soc. Hort. Sci., 50(2), 262-269.    Non-patent Literature 2: MATSUO, Tomoaki and ITOO, Saburo (1981b): A Simple and Rapid Purification Method of Condensed Tannins from Several Young Fruits. Agric. Biol. Chem., 45(8), 1885-1887.
It is an object of the present invention to provide an antiviral agent that has an excellent inactivating action on non-enveloped viruses and that is highly safe for the human body, and an antiviral composition containing the antiviral agent and useful for disinfection for the viruses and prevention of infection of the viruses.